1. Field of the Invention
The present invention relates to alkylation reactions to prepare ethylbenzene. More particularly, the invention relates to a catalyst and reactor system to prepare ethylbenzene.
2. Background of the Art
Ethylbenzene is an important product with a variety of uses including, in particular, as a precursor for styrene production. While a wide variety of preparation routes may be employed, one commonly employed method is a simple liquid phase alkylation of benzene with ethylene that is usually promoted with conventional acidic catalysts, such as Friedel-Crafts type catalysts, and in particular with aluminum trichloride catalyst. Because this method has been known for many years, many commercial production facilities have been designed toward its use. Thus, this method is still used to prepare billions of pounds of ethylbenzene every year.
Unfortunately, aluminum trichloride is an extremely corrosive material. Thus, its use presents very significant safety and environmental problems. It must be handled very carefully and, like most catalysts, it is typically recycled to improve production economics. Even with recycle, however, a proportion is always lost in the hydrocarbon product and must then be neutralized with caustic and, ultimately, removed, thus presenting a waste problem. Finally, because of its extreme corrosivity, its use is restricted to reactors made of special alloys. These reactors typically cost several times more than conventional stainless steel reactors of equivalent dimensions.
Alkylation may also be performed in a multiple fixed bed reactor system.
These fixed bed designs have been found to be useful for alternative liquid and gas phase methods for preparing ethylbenzene. The fixed beds frequently include supported catalysts. However, because of the limited solubility of ethylene in benzene, many fixed beds are needed to ensure an overall low ratio of benzene to ethylene.
It would therefore be desirable in the art to provide a method and means of preparing ethylbenzene that avoids use of corrosive or otherwise dangerous catalysts such as aluminum trichloride, and that may be used in the existing alkylation reactor units including those that have historically been used for conventional Friedel-Crafts type alkylations of benzene with ethylene. It would also be desirable for such alkylation to be able to be carried out at relatively low benzene to ethylene ratios.